(1) Field of the Invention
This invention relates to a communication device provided in a base station for cellular phones, and more particularly to a communication device which generates heat.
(2) Description of the Related Art
The usage rate of cellular phones has been becoming so high that communication devices used in base stations are demanded to be higher in output. Communication devices higher in output generate larger amounts of heat, which affect reliability of operations thereof. Therefore, how to attain efficient heat dissipation is a key problem of recent communication devices. Provision of heat-dissipating fins is among conventional solutions thereto.
In conventional communication devices, a single heat-dissipating fin section, for example, is provided for each heat-generating electronic module (see e.g. page 3 and FIGS. 1 and 2 of Japanese Unexamined Patent Publication No. 6-310883). Further, on electronic modules different in the amount of heat generation, there are mounted respective single heat-dissipating fin sections which are different in the height of fins (see e.g. page 6 and FIG. 10 of Japanese Unexamined Patent Publication No. 11-298180).
FIG. 17 is a perspective view showing an example of a conventional communication device having a heat-dissipating fin section attached thereto. FIG. 18 is an exploded perspective view of the conventional communication device shown in FIG. 17 with a digital distortion-compensating unit and a converter unit removed therefrom. FIG. 19 is an exploded perspective view of the conventional communication device with a power supply unit further removed from the apparatus in the state shown in FIG. 18.
As shown in FIGS. 17 to 19, the communication device 100 is comprised of a heat-dissipating fin section 101, a digital distortion-compensating unit 102, a converter unit 103, power supply units 104, 105, a power amplifier unit 106, and a front panel 107.
The heat-dissipating fin section 101 is comprised of an aluminum heat-receiving plate and a plurality of aluminum fins protruding therefrom. The power supply unit 105 and the power amplifier unit 106 are mounted on the heat-receiving plate. The heat-dissipating fin section 101 dissipates heat generated by the power supply unit 105 and the power amplifier unit 106. The heat-dissipating fin section 101 has a generally rectangular parallelepiped shape, and extends over the entire surface of one side of the communication device 100.
The digital distortion-compensating unit 102 is a printed board on which is mounted a circuit for compensating for distortions of a digital signal. The digital distortion-compensating unit 102 is mounted on the heat-dissipating fin section 101 in a manner covering the power supply unit 104 mounted on the heat-dissipating fin section 101.
The converter unit 103 is a printed board on which is mounted a circuit for frequency conversion of a signal.
The power supply unit 104 is a printed board on which is mounted a circuit for supplying power to circuits. The power supply unit 105 is a packaged power supply module which supplies power to circuits. The power supply unit 104 is mounted on the heat-dissipating fin section 101 in a manner covering the power supply unit 105 and the power amplifier unit 106 mounted on the heat-dissipating fin section 101.
The power amplifier unit 106 is an L-shaped printed board on which is mounted a circuit for amplifying a high-frequency signal. This printed board has power transistors mounted thereon for amplifying the high-frequency signal.
The front panel 107 is a panel attached to a front side of the communication device 100 when it is received in the rack.
Heat generated by the power supply unit 105 and the power amplifier unit 106 is dissipated by the heat-dissipating fin section 101, whereby the temperature of the communication device 100 is prevented from rising beyond a predetermined temperature. In the communication device 100 constructed as above, when the amount of heat generated by the power supply unit 105 and the power amplifier unit 106 is increased, it is necessary to increase the area of the heat-receiving plate of the heat-dissipating fin section 101, and the height and length of the fins to enhance the heat dissipation efficiency.
Now, heat emitted from power transistors is very large, and by far larger than heat emitted from power supply circuits or the like. Therefore, heat emitted from the power amplifier unit 106 having the power transistors mounted thereon is larger than heat emitted from the power supply unit 105, which prevents heat from being uniformly distributed in the heat-receiving plate of the heat-dissipating fin section 101. Further, non-uniform heat distribution is also caused depending on the mounting locations of the power transistors. Therefore, to simply increase the size of the heat-dissipating fin section 101 is not enough, for example, to realize uniform heat distribution all over the heat-dissipating fin section 101 and conduction of heat to the distal ends of fins.
As described above, although the size of the heat-dissipating fin section is increased for coping with an increase in the amount of heat generation caused by the increased output, heat locally emitted from the heat-generating portions of the apparatus is not uniformly conducted to the entire heat-dissipating fin section, so that some fins do not serve the function of dissipating heat, which degrades the heat dissipation efficiency. Further, there is a demand for a communication device small in size and weight so as to facilitate maintenance and mounting of the apparatus in a rack.